1. Field of the Invention
The present invention relates to a zoom lens and an image pickup device including the same, and is, for instance, suitable for an image pickup optical system of a video camera, a digital still camera, a TV camera, a monitoring camera, or a silver halide photographic camera.
2. Description of the Related Art
An image pickup optical system adopted in an image pickup device is required to have a high zoom ratio and be a small zoom lens. The system is also required to be a retractable zoom lens that contracts the intervals between lens units in a non-imaging state so as to be different from intervals in an imaging state, and allow the thickness of the image pickup device to be reduced. U.S. Patent Application Laid-Open No. 2011/0234882 and U.S. Pat. No. 7,738,181 disclose four-unit zoom lenses that include, in order from an object side to an image side: a first lens unit having a positive refractive power; a second lens unit having a negative refractive power; a third lens unit having a positive refractive power; and a fourth lens unit having a positive refractive power.
U.S. Pat. No. 6,978,089 discloses a zoom lens that retracts a part of lens units away from the optical axis in a retracted state so as to reduce the thickness of the entire device during a non-imaging state.